TRANSFORMING SUBURBIA SUPURBIA SEMI

Transcription

TRANSFORMING
SUBURBIA
SUPURBIA
SEMI-PERMISSIVE
2015
TRANSFORMING
SUBURBIA
SUPURBIA
SEMI-PERMISSIVE
Contents
Foreword: Peter Murray
Executive Summary
About this report and its authors
Introduction
Supurbia
Semi-permissive
16 ideas for transforming Metroland
Creating value in suburbia
Credits
Supurbia | Semi-permissive
1
Foreword: Peter Murray
I am lucky enough to live in a suburb, and a very special
one at that. Bedford Park is the ‘first garden suburb’ it was a precursor of the Garden City movement and of
developments such as Hampstead Garden Suburb and
Brentham. It sports tree-lined streets, front and back
gardens and distinctive fences. The majority of the houses,
detached and semi-detached, were designed by R Norman
Shaw in the Queen Anne style and built of bright red bricks
fired in local kilns. It is low density.
Since it was built in the latter part of the 19th century
there have been various phases of increasing that density.
The Edwardians built two new mansion blocks. They
are four storey rather than the two and three storeys of
the surrounding houses, and they deliver 16 generous
apartments where there would be four family houses.
In the 1930s a single large house, built for Jonathan Carr,
the developer of the suburb, was demolished to make
way for a block of older persons flats. Then in the 1950s
and early sixties Acton Borough Council implemented
a programme of demolishing the then rather run down
houses and replacing them with blocks of flats. A single
plot could deliver up to 20 new units over five floors.
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The vandalism of the Council in demolishing important
Norman Shaw houses so upset the locals that they set
up an amenity society to protect them and as a result the
majority of houses on the estate were listed in 1967 and
the densification programme was halted.
Densification of suburbs is not new and done appropriately
it works. It also has real benefits to the local community in
providing a richer mix of types and sizes of accommodation
to suit different lifestyles. Very importantly, it needs
to be done with the consent of the local community;
London’s suburban residents are famously sensitive about
development in their back yards.
That is why the well considered approaches to densifying
London’s suburbs illustrated in this book are so important.
Suburban sprawl is an inherently inefficient use of land
- the capital’s most valuable resource. As the ideas on
the following pages show, well considered replanning and
densification of suburban areas can make a substantial
contribution to the delivery of much-needed homes for
Londoners. Not only can it deliver large numbers of homes
but it can also help to regenerate the lacklustre economies
of London’s towns and high streets.
Executive Summary
For all their virtues, the inter-war suburbs need to change
- they are land-hungry, energy-hungry and car-dependent
– but local democracy and owner-occupation make large
scale change almost impossible.
How can we modernise the suburbs, increase the number
and variety of homes and reduce car dependence – but
maintain the space, greenery and independence that
people value?
This report shows how urban intensification of suburban
London can increase housing supply, promote economic
activity, improve local service provision and reduce
congestion – whilst improving the quality of life, the
choices available and the sustainability of the suburbs.
Doubling the density of just 10% of the outer London
Boroughs could create one million new homes.
Suburbia
Supurbia is a strategy for intensifying London’s suburbs
that balances their inherent advantages with higher density
and amenity value. Its approach is twofold: redeveloping
the local main streets and parades as mixed-use places
with increased housing, improved service and amenity
provision; and enabling owner-occupiers to develop their
land, creating rich diversities of housing. The strategy
will bring together local authorities and communities to
plan appropriate developments, and allow homeowners to
release equity in their land for home improvements. It will
also reduce reliance on mainstream developers to ease
the housing crisis, providing an approach that is more
adaptable to communities’ needs.
Semi-permissive
Permitted development rights can incentivise
suburban householders to collaborate in replacing and
supplementing their houses with modern homes. Giving
suburban householders a vested interest in development
could help to overcome resistance to change.
There are over 725,000 semi-detached and detached
houses in the outer London Boroughs. This scheme
could create over 100,000 additional homes and renew
a similar number.
16 Ideas for transforming Metroland
The original report Supurbia: a study in urban
intensification in Outer London was produced by HTA
Design LLP in 2014.
It asked: how might suburban transformation be triggered,
what incentives might begin to unlock the potential? Is
there a case for special measures based on the principle
of Housing Zones proposed in the GLA’s Housing Strategy?
Or should the incentives be more generally applied across
the outer Boroughs and London as a whole?
The study made 16 preliminary proposals for further
discussion. Many of these have been developed further
in this latest report and in submissions to the NLA’s New
Ideas for London Insight Study.
Creating value in suburbia
The place potential of well connected areas of metroland
makes possible value uplift associated with the Supurbia
vision. According to Savills, the gross development value
generated by homeowners who club together to develop
their plots could be as much as 60% - a considerable
incentive for change.
3
About this report and its authors
This report has been produced by HTA Design LLP and
Pollard Thomas Edwards (PTE), with support from Savills
and Nathaniel Lichfield and Partners.
It has grown out of an earlier report - Supurbia: a study in
urban intensification in Outer London produced by HTA in
2014 – and from recent submissions by both practices to
the NLA’s New Ideas for London Insight Study. The report
contained input from Savills on delivery and viability.
HTA’s Supurbia - one of the ten winning entries to the NLA
competition – covers a wide range of potential initiatives
to transform the suburbs. Supurbia is offered here as an
umbrella title not only for the ideas set out below, but also
for other contributors to bring forward their own
proposals.
4
Semi-permissive is Pollard Thomas Edwards’s more
detailed proposal to use carefully-framed permitted
development rights to bring about beneficial change and to
incentivise householders to become micro-developers.
PTE was supported by planning consultants Nathaniel
Lichfield and Partners.
The two approaches have much in common, but also
show distinctively different attitudes to planning and
delivery: PTE and NLP propose a more market-led
approach facilitated by top-down planning reforms, while
HTA propose a more consensual approach based on
neighbourhood planning and local development orders.
We have found the debate stimulating: we hope that the
readers of this report will add their own contributions
through our website.
Both Supurbia and Semi-permissive envisage a reduction in car
domination and the greening of streetscapes
5
Introduction
The Metroland problem
When London’s Metroland was first developed in the early
20th century, it was conceived as an affordable means
of access to London’s booming economy for working
Londoners. It was popular, successful and gave rise to a
culture all of its own, perhaps best characterised by the
late British poet laureate, Sir John Betjeman in his 1973
documentary film, Metro-Land, made for BBC, and in
various evocative poems, including ‘Middlesex’; ‘Gaily into
Ruislip gardens / runs the red electric train...’
A century later, perceptions of some areas of outer London
have deteriorated and some suburbs are under-performing
by comparison with central London, lagging behind in job
creation, average incomes and property values. According
to the Smith Institute ‘Towards a Suburban Renaissance’
levels of poverty were still growing in outer London suburbs
in 2014, whilst remaining stable in central London during
the same period.
Supurbia is an idea that recognises that the capacity
to increase supply identified in the recent Strategic
Housing Land Availability Assessment (SHLAA) for London
already includes the contribution of all currently identified
brownfield sites, infill sites, redeveloped local authority
stock and redeveloped industrial land. So the Supurbia
idea instead concentrates on the capacity of the three
quarters of a million privately owned semi-detached
houses in outer London. Whilst once the suburban ideal,
there has been some loss of original character, as front
gardens have been converted for parking and verges and
trees lost to hardstanding. Moreover, changes in household
makeup mean that ever fewer households really benefit
from their space.
These homes are not only low density - typically averaging
only 25 - 35 homes per hectare - but amongst the most
under-occupied. Nearly 40% of owner-occupier
6
households (often ‘empty nesters’) have at least two
spare bedrooms, while sharing groups who increasingly
rent suburban homes rarely take full advantage of large
gardens. In Bexley, based on the 2011 Census data, 45%
of the population inhabit the ubiquitous three bed semi.
60% of the households comprise two persons or less,
80% are owner occupiers, 66% own cars, 24% own two
or more cars. In one neighbourhood of three and four
bedroom semis in Bexleyheath, which we examined as a
pilot, we estimated that 38 households comprised 110
people including only 18 children, or 2.9 people per 3- or
4-bedroomed home.
At the same time, occupants of the suburbs are famously
resistant to changes that might unlock the vast potential of
this huge area of low density city. According to The Centre
for London, 75% of people in outer London Boroughs
(compared to 50% in inner London) oppose new housing
development in their neighbourhoods. The politics and
planning of housing
development now favour
the rights of those
who are well housed to
resist development in
their neighbourhoods
to meet the needs of
those who are not. This
phenomenon is now
evident in all sectors of
society, not just amongst
the well-resourced middle
classes.
The Supurbia project
examines how financial
self-interest could be one
way of stimulating change
and delivering new housing development. The potential
prize is great: doubling the density of just 10% of the
outer London Boroughs would create the capacity for one
million new homes - the area covered is simply huge and
the capacity so correspondingly great that it should not
be overlooked, either by the Local Authorities concerned
or by the Mayor of London, who seek to find solutions to
London’s housing crisis.
But how might such changes be triggered and what
incentives might begin to unlock the potential? And is there
a case for targeted measures based on the principle of
Housing Zones proposed in the GLA’s Housing Strategy, or
should the incentives be more generally applied across the
outer Boroughs and London as a whole?
Metroland’s Potential
The objective of Supurbia is to build on the inherent quality
of the suburbs (individual homes on their own plots with
parking, easy access to public and private open space set
in a verdant environment) with a set of policies targeted at
meeting popular aspirations. The underlying premise
is that by offering people choices that are currently
denied them, a notoriously static situation might be
transformed into a dynamic one. A programme of urban
intensification might trigger changes resulting in a much
improved fit of population to its accommodation; that is
more sustainable, efficient, affordable and desirable. The
intended outcome is both an increase in housing supply
and a more visually pleasing, greener urban environment.
This should come alongside an improvement in economic
activity, local service provision and reduction in energy
use and congestion. In all, an improved quality of life for
London’s suburbanites.
a paradise lost; once tree-lined streets are now tree-less,
what were front gardens are now concreted driveways,
and homes have such low rates of occupancy that local
services struggle and trade dies in local parades awash
with cheap take-away joints and pound shops.
The Supurbia idea sets out to re-imagine such
neighbourhoods with greater population density, better
fitted to the available accommodation and creating
improved commercial footfall for improved local
services and safer streets. Our calculations show how
contemporary building and public realm design, and
standards of construction can also dramatically reduce
energy use and increase biodiversity. Similarly, techniques
of neighbourhood infrastructure design and management
can redistribute supply and demand to avoid the necessity
of major infrastructure replacement and renewal.
Paradise Lost - the qualities of suburbia have been eroded over
time in some areas
Some of the neighbourhoods we have examined as
potential pilot areas are decidedly sub-topian examples of
7
Supurbia
Transforming Metroland
The main Supurbia idea addresses the streets of semidetached housing behind main roads. With an estimated
24% of London’s land classified as rear gardens, suburban
plots consume a disproportionate amount of land. The
typical suburban plot, at 8m wide and 40m deep, often
accommodates no more than a two storey house with
a footprint of 7.5m by 6m. So a mere 15% of the plot is
actually built on, which could easily rise to 30%, not only
leaving plenty of green space as gardens but potentially
without any loss of greenspace - replacing large sheds
with new homes and grassing over concrete verges are
some obvious examples. These plots and the houses
that sit on them also display a remarkable degree of
consistency owing to the standardisation of approach
adopted by their developers – often Wates and John
Laing, the leading housing developers of the inter-war
years. This uniformity lends itself to a standardised
design-led approach to augment the housing provision that
is described in what follows.
The vision for intensifying suburban London with consistent
high quality development is for the Local Planning
Authorities and the local residents within a neighbourhood
to work together with a lead facilitator to draw up
suitable and agreeable options for the redevelopment of
privately owned properties, and of the public realm in the
wider neighbourhood area. These would then be worked
into a “Local Development Order”. Local Development
Orders (LDOs) are a mechanism by which a range of
such standard design solutions can be pre-approved
(i.e. granted planning permission) so as to create options
from which householders can select their preference,
without again having to apply for planning permission
at a future date - more or less equivalent to permitted
development. LDOs are applied to a defined area such as
a neighbourhood or block.
8
To begin the process, Local Planning Authorities could take
a consultative, pro-active, but more hands-on approach
in partnering with developers and off-site manufacturers,
whilst ensuring that local residents are fully engaged and
on board from the initial stages of working on the Local
Development Orders. In this way householders would have
early input on the materials palette and design options
that would be suited to a particular area. These would
then be incorporated into Local Plans. Under this route it
is important that residents buy into the proposals and are
closely involved with them from the beginning.
But actually Neighbourhood Planning might well be
the main route to the designation of such areas within
Local Plans. For Neighbourhood Planning a group would
have to be formally established and the neighbourhood
boundaries approved by the local authority. Aside from the
potential cost of extensive consultation the Neighbourhood
Plan would have to be approved via a neighbourhood
referendum. Again, Local Planning Authorities could
proactively encourage the formation of such groups but
they could be more hands off in driving the process. Either way, we suggest that the costs of such processes
could be met by the promoters of the redevelopment or
those of major regeneration schemes seeking to engage
with surrounding neighbourhoods.
The process of creating a Local Development Order
would bring into being a range of “plot passports” (a
form of permitted development) for all homeowners in
the neighbourhood. Plot Passports would be a menu of
redevelopment options available for all homeowners within
the neighbourhood to redevelop their property. They could
exercise these options if they wanted to, but equally they
could refrain from doing so, if they did not want their
property redeveloped. Importantly one homeowner
refraining does not prevent another homeowner from going
ahead, though it does obviously prevent the collaborative
options with their immediate neighbours.
Just as importantly, though, it raises the opportunity
for the owner of a single semi-detached house, or a
pair of neighbouring or facing owners where there was
collaboration between them, to exercise choices by
developing their land to suit their needs; new family homes,
bungalows or flats over garaging in rear gardens, or the
redevelopment of pairs of existing semi-detached homes
on existing street frontages. Each passport would also
contain a solution that could be adopted to intensifying
back garden land, depending on the degree to which
householders would like to take up the opportunity on their
land alone. We illustrate a possible range of plot passport
options for existing semi-detached homeowners in the
adjacent diagrams.
Transforming an existing rear access into a mews design that maximises private amenity space and avoids overlooking
9
The drawing below shows an area of South London with
a typical range of suburban block typologies which would
be suitable in principle for this treatment - some with rear
access lanes between opposing back gardens, many with
plots deep enough to permit rear garden development of
the type we envisage. Having analysed such plots, we
would have a set of suitable solutions for intensification.
All in all, our illustrative block begins with a density of 33
homes per hectare - a typically low suburban density. If a
quarter of all plots added one dwelling, the density would
increase to 45 homes per hectare. Logistically we could
intensify 10% of outer London boroughs every 10 years.
Illustration of a typical low density suburban blocks in outer London
10
Initially the Supurbia policy would be about focused,
area-based, schemes centred on under-developed
transport hubs where urbanisation in a concentric pattern
could create outward moving contours of increased
value, like the ripples in a pond, triggering the take up of
intensification schemes in a variety of typologies. This
could transform the poorer, often subtopian areas of
London’s heavily concreted and low density suburbia into
a vision of thriving, vibrant and sustainable placemaking –
the Supurbian vision.
Supurbia - greening of previously car dominated public realm
Making it happen
Financial incentives for homeowners
For each of the options illustrated we have evaluated
the increase of value achieved as a consequence of
development by individual homeowners, netting off
development costs, and any value reductions occasioned
by the reduction in garden sizes. The results indicate
a realistic level of financial incentive for homeowners
to exercise their redevelopment options in most cases.
Land would thus be intensified while preserving buildings’
individuality, and owner-occupiers could unlock the equity
in their unused land and invest it in their home, raising
the quality of housing across the neighbourhood and
improving the street as front plots are renovated and the
neighbourhood area improved (i.e. reinstating tree-lined
streets) as part of the redevelopment. Our preliminary studies reveal that homeowners may
stand to benefit from net development profits of between
£110,000 and £210,000 per household, depending on the
redevelopment option and typology adopted.
Changes to planning
The Treasury’s Productivity Plan published on the 10th
of July 2015 made it clear that the Government sees
the solution to the country’s housing problem in the
development of brownfield land via automatic permission
for housing on such sites. But there are good reasons why
brownfield land often remains undeveloped: being heavily
contaminated and/or cut off from good access to public
transport, the creation of well designed, good quality,
popular and affordable housing without vast upfront
investment and years of costly remediation seems a bit of
a leap of faith. Back garden land is generally protected, but not all
London boroughs take an entirely protectionist approach.
Back garden land has been given added protection in
the National Planning Policy Framework (NPPF) when it
was reclassified from brownfield to formerly undeveloped
land. However, the NPPF makes it clear that the key
consideration should be whether back garden development
would harm local character. We are not advocating a free
for all; we believe a carefully considered design-led and
consultative approach could improve the character of
certain suburban areas.
Householders already have a wide range of permitted
development rights, such as the ability to extend their
homes up to 50% of the curtilage of the original house,
back/side extensions up to 6 metres in the case of semidetached and terraced homes from the closest back wall
to the house (8 metres in the case of detached homes),
loft extensions up to 40 cubic metres in the case of
terraced homes and 50 cubic metres in the case of
detached homes.
11
Plot Passport
The plot passport concept is
drawn from our experience of the
emerging custom build market,
applicable because of the generic
standardisation of the 1930s
semi-detached type.
12
Example 1
Self Build Single Plot Intensification
This single plot intensification retains the main
house garden up to 10m or 12m. Options show a
new 2-storey, 2 bedroom mews house averaging
72sqm. Depending on the context and relationship
to the main house, the design of the new mews
houses are sited to the rear or front of the new
plot with their private amenity space taking up
the remainder.
The range of options illustrated create one
additional home and a typical profit of £140,000
for the homeowner.
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Example 2
Self Build Double/Facing Plot Intensification
The double plot intensification of facing homes,
which share a driveway, enables the creation of
a third plot at the back that utilises a portion of
garden space from each of the two main homes.
The illustrated options show a double storey mews
house, a flat above garages (one for each of the
existing and new dwellings) and a single storey
accessible dwelling. The options range in size from
72 to 90 sqm.
The range of options create one additional home
and a typical profit of £110,000 for the homeowners.
14
Example 3
Self Build Double/Paired Plot Intensification
The double plot intensification of paired homes
enables the replacement of the two existing
dwellings with an entirely new development that
can provide a new block of flats or townhouses
fronting the streets, with new garden houses to the
rear overlooking the amenity spaces. The options
present a range of shared or private amenity space
arrangements and parking solutions.
These example illustrate either 4 or 5 new homes
(with a net gain of 2 to 3 homes) and a typical profit
of £210,000 for the homeowners.
15
The Supurbia concept envisages suburban improvement
areas where a cocktail of policy initiatives including
area based local development orders (and possibly
local referenda, through neighbourhood planning). Plot
Passports enable the gradual take-up of development
opportunities as household circumstances permit.
Public realm improvements further enhance the
neighbourhood environment.
16
However, the current permitted planning rules do not
allow for buildings to be constructed within the land that
surrounds a house for the purpose of being lived in
(i.e. having a plumbed-in and self contained bathroom
and/or kitchen).
New measures announced in the Productivity Plan will
include permitted development rights to extend up to the
height of neighbouring buildings - if neighbours do not
object. A lot of these measures do not necessarily allow
for a well-considered approach to achieving high quality
design; resulting in a widely eclectic, piecemeal and at
times not ideal intensification of suburban areas.
Back gardens are widely valued because of their
contribution to biodiversity. However, the development
of back gardens does not mean that equal or increased
amounts of biodiverse rich landscaping could not be put
back on site – particularly with the use of living roof
coverings such as the increasingly popular sedum.
So the permitted development rules should be changed
to allow self-contained homes to be built on the land
surrounding an existing house, where the design
specification has been agreed with the neighbourhood,
most probably through the neighbourhood plan.
Before
Funding the creation of Plot Passports in a
neighbourhood
Outer London is now peppered with an increasing array
of housing zones, opportunity areas, local authority
estate redevelopments and major bownfield developments,
particularly around new transport infrastructure
investment. Many, if not most of these can seem like
incongrous islands of high density threatening to overbear
on the surrounding suburban neighbourhoods. It’s not
uncommon for the density of such projects to rise to 350
homes per hectare - so called ‘superdensities’ that
exceed the density of surrounding neighbourhoods by
ten times or more.
We envisage that the joint venture partnerships of local
authorities, developers and housing providers that have to
come together to deliver these gargantuan projects may
see the virtue of engaging with the populations of
the surrounding suburban hinterland of their developments,
many of whom can otherwise be in entrenched opposition
to what may seem to them to be interloping alien
developments. In our experience opposition and support
are opposite sides of the same coin and one can turn to
the other if only there is the appropriate incentive.
So these consortia may well be willing to sponsor
neighbourhood planning in the interests not only quelling
potential opposition, but also because participation in
urban intensification around their projects would be a way
of adding value to their investment. If so, we foresee the
identification of suitable pilot areas, the collaboration of
After
Many two storey shopping parades have the capacity for redevelopment suitable for both millennials and empty nesters, liberating the suburban
hinterland for family accommodation.
17
local authorities and sponsorship of community advocates
to undertake Neighbourhood Planning exercises designed
to nest suburban improvement areas within Local Plans.
The design-led approach
The next stage is the development and testing of designs
for the range of typologies we have illustrated in more
detail. This is a design-led and technical process in which
the procurement and constructional issues would be
flushed out. The premise is that the standardised nature
of semi-detached suburbia is such that this exercise will
produce a range of standard solutions capable of meeting
the regulatory challenge in most of the circumstances
that can be foreseen. These solutions would therefore
become standard templates suitable for adoption within
the framework of Local Development Orders - enabling the
rapid adoption of pre-approved typologies in a wide range
of settings.
Analysis of plots would produce sets of suitable solutions
for intensification of back garden land and redevelopment
of existing buildings, indicated on plot passports
comparable to outline planning permissions. These would
incorporate planning considerations such as sunlight/
daylight, back-to-back distances, retention of valuable
trees and suitable amounts of open space, and could
give guidelines on how to reinvest a portion of gain from
development into improving the environmental efficiency
of main houses. Each passport would contain a range of
parameters and solutions for intensifying back garden land
and redeveloping existing buildings.
Property owners could select a pre-approved option or
customise one within the set parameters, either developing
their land alone or in collaboration with neighbours where
this was an option. This concept builds on the current
approach of both permitted development rights and
forthcoming zoning for brownfield land; local authorities
would provide additional amenities as intensification
reached agreed thresholds. Each improvement will have
been agreed through the Local Development Orders and
tied to income generated through the development process
and additional council tax revenue.
Tax Increment Financing might become the method
for funding improvements to neighbourhood energy
systems and area improvements to public realm that we
envisage as part of the process of achieving a significant
improvement to neighbourhood quality to accompany the
investment in individual and groups of private homes.
This process enriches limited suburban housing stock with
a spectrum of options. Instead of the undifferentiated
one and two bedroom homes that dominate many large
scale developments, this will include family homes with
gardens, investor PRS schemes, accessible ground floor
older people’s accommodation (bungalows) and affordable
starter houses for young households. Plot passports will
New family homes accessed from existing frontages designed to maximise the private amenity, and eliminate overlooking
18
Supurbia will be a more socially inclusive and convivial environment
enable local authorities to agree parameters on the range
of sites within a neighbourhood, optimising quantum and
mix of development. This provides opportunities to speed
investment from custom build to small investors and
builders.
A new breed of SME in high quality offsite
manufactured homes
The plot passport menu of options would comprise online
design catalogues for homeowners to choose high quality,
pre-manufactured yet durable housing options exceeding
London standards. Groundwork can be minimised through
the use of lightweight prefabricated structures and the
experience of construction using pre-manufactured
structural insulated panels (SIPS) is that disruption is
minimal. These techniques would maximise speed and
minimise inconvenience of construction, helping to preserve
existing communities and taking full advantage of the preexistence of all necessary infrastructure.
This makes room for niche developers that already
specialise in custom built or pre-manufactured houses to
grow into the market and work with local authorities and
communities to continue the development of the different
house types. This takes the onus of easing the housing
crisis off large-scale speculative development, which
often faces huge obstacles in terms of funding and
community opposition, introducing a steadier stream of
housing supply into the market. In addition, it champions
the needs and characters of local communities and
preserves the qualities that make London’s suburbs so
popular, while combining them with the vibrancy and
convenience of the city centre.
Conclusion
As well as increasing housing supply and improving
London’s suburbs, the Supurbia concept has the capacity
to liberate equity locked up in relatively poor quality private
housing stock by facilitating home owners to participate in
profitable development which will also increase supply and
improve neighbourhoods. The design-led approach, based
on Local Development Orders and prior approval of plot
passports would guarantee a high quality outcome.
We recommend pilot studies, located in the hinterland of
large scale urban regeneration schemes in London that
would enable local people to participate in the betterment
of their neighbourhoods and thus become advocates for,
rather than opponents of, urban intensification and new
housing development, turning NIMBYism on its head or
turning NIMBY’s into YIMBY’s (Yes – in my back yard!)
19
Semi-permissive
The challenge
London’s biggest building boom took place in the 1920’s
and 30’s, with massive expansion of the suburbs around
new commuter rail and underground links. The great
architectural legacy of Metroland is the semi-detached
house. There are around 541,000 semi-detached
dwellings in the outer London Boroughs, and over 176,000
detached houses.
The form was pioneered by distinguished architects
and planners of the Arts & Crafts and Garden City
movements, and popularised by the developers of By-pass
Tudorbethan. They all extol the merits of a house with its
own front door, and gardens front and rear. Pairing offers
the appearance and status of a ‘villa’ and the practical
benefits of a garden-passage and side-windows – at a
lower development cost than a detached house.
The semi has been celebrated in popular culture, from John
Betjeman and Osbert Lancaster to the Bonzo Dog DooDah Band and The Good Life.
the street-scene, destroying privet hedges and cherry
trees. The side passage is less important now that we have
stopped digging for victory and feeding coal-fired boilers.
The admirable flexibility of the semi to suit growing and
shrinking families becomes a problem in a time of housing
pressure. Many suburban homes are under-occupied: if
empty-nesters could realise some value from their asset,
move into a more convenient home and free-up a family
dwelling then everyone wins. Conversely, in some areas
privately rented semis in multiple occupation provide
overcrowded and insanitary living conditions.
Politicians and planners are very reluctant to promote
change in the suburbs, and suburban voters are fiercely
protective of the status quo. The pattern of individual
freeholds and predominance of owner-occupation
contribute to community cohesion, but make large scale
change almost impossible.
For all its virtues the inter-war suburban semi is in some
respects an outmoded dwelling type for 21st century
London. It is land-hungry and energy-hungry and
encourages car dependence. Car-cramming has disfigured
So, how can we modernise the suburbs? How can we
update the building stock to modern standards, increase
the number and variety of homes, reduce car dependence
– and yet retain the characteristics of space and greenery,
privacy and independence that people value?
The vision ...
... The reality in some areas of outer London
20
Our solution
Our proposal is to use permitted development rights to
incentivise the owners of semis (and detached homeowners also) to collaborate to replace or supplement their
two houses with additional modern homes – development
will be semi-permitted. It builds on the wider-ranging work
by HTA on Supurbia, and it works like this.
Owners of adjoining semis (sharing a party wall) would be
permitted to redevelop or radically remodel their houses to
create three or more modern homes.
Owners of neighbouring semis (removing their party fence
and combining their side passages) would be permitted
to develop one or more single-storey courtyard house at
the rear. Our proposal would lift the blanket restriction on
‘garden grabbing’ and extend permitted development with a
more intelligent approach.
We have modelled six scenarios based on a pair of typical
suburban house plots, and creating between one and five
additional homes.
Pre-conditions
Our proposal is to establish a Prior Approval process
under the Town and Country Planning General Permitted
Development Order 1995. It would apply in the following
circumstances:
There must be a net increase in residential dwellings
Developments must be within 800m of a tube or
railway station
Land in the Green Belt is excluded
The Rules
Permitted Development must not be hampered by overcomplex rules or subjective approvals. On the other hand,
a few simple rules can ensure that a decent standard of
design is achieved. These need to be measurable, easily
understood by the applicant and easily checked by an
approved inspector. Permitted development should improve
the appearance and sustainability of its setting, not
damage them.
Transport
Given the requirement to be within 10 minutes walk of
a station, a reduction in car parking will be acceptable
subject to a Controlled Parking Zone being in place or
being created. Capped financial contributions towards
a CPZ and Car Club may be required. Cycle parking is
required in line with existing policies.
Flooding
Within Flood Zone 2 or 3 a Flood Risk Assessment
is required.
Design
The GLA would prepare a Supplementary Planning
Document (SPD) providing minimum design standards for
Semi-Permissive development. A Design Statement must
accompany the Prior Approval application.
Financial contributions
Unless a local CIL is in place, a Section 106 Agreement
on a standard template will cover transport and affordable
housing obligations where required. A financial contribution
to affordable housing would be set at a standard rate per
additional home created.
Conservation Areas, statutorily and locally listed
buildings are excluded
The presumption is that approval will be granted subject
to the verifiable checks set out below.
21
The benefits
Semi-permissive development could make a significant
contribution to housing delivery in London, and it can
be implemented quickly and easily working within the
established planning system.
Approximately 40% of land in outer London falls within
800m of a local station, which suggests that around
287,000 existing houses meet the location requirement.
If just 10% of owners brought forward proposals to
double the homes on their plot, this would create 72,500
additional homes and renew a similar number. A 15% takeup coupled with our more ambitious design scenarios could
create over 200,000 additional homes.
New and remodelled homes would comply with modern
technical, access and space standards, including energy
standards. (Anyone who has lived with draughty Crittall
windows knows how uncomfortable and costly to run a
1930’s house can be).
The location and transport criteria will help to reduce car
dependence and parking blight.
The scheme will generate work for small builders and local
design and planning professionals.
Our proposals will provide a strong financial incentive for
collaborating owners to help solve London’s housing crisis.
We expand on this with the Development Appraisal that
follows.
What next?
The GLA is asked to endorse the scheme and fund
research and development of a pilot scheme in a
designated area.
Existing Homes *
Detached
180,000
Semi-detached
550,000
Total
730,000
Net Additional New Homes
Participation
rate
One additonal home
per existing house
Two additional homes
per existing house
5%
36,500
73,000
10%
73,000
146,000
15%
109,500
219,000
Net Additional New Homes (Barnet and Ealing)
Participation
rate
Scenario
A
Scenario
B
Scenario
C
Scenario
D
2 become 3
2 become 4
2 become
6
A, B and C
combined
5%
1,369
2,738
5,477
3,195
10%
2,738
5,477
10,954
6,390
15%
4,107
8,215
16,431
9,585
* Based on 2011 census and 2014 household data of
outer London boroughs only
Applying the pre-conditions to sample boroughs
22
Scenario 1 - two become three
The scenarios for change are based on
a typical outer London suburban street
of semi-detached houses with on-plot
parking. Plot width is 9.0 metres and
garden length is 15.0 metres. Existing
houses are 2.5 storeys with four bedrooms
and around 135 sqm floor space.
In scenario 1, neighbouring owners
collaborate to combine their gardens and
remodel their side-passages, creating
access to a new single-storey house
located in the rear garden. At 75 sqm
the new house has two bedrooms and
is wheelchair adaptable, making it ideal
for older downsizers or for a small family.
The existing and new properties each has
a 30 sqm garden. The new house has a
green roof and its outlook is into its own
courtyard gardens, minimising impact on
neighbours. There is no demolition of the
existing homes.
Many existing suburban houses have
larger gardens, which may enable the
insertion of two houses rather than the
one shown here.
23
Scenario 2 - two become three
Two adjoining semis are replaced by three
terraced houses, each with front and rear
gardens and roof terraces. Internal plot
width is 4.8 metres and total floorspace is
145 sqm including a second floor mansard,
providing space for four bedrooms or more.
24
Scenario 3 - two become four
Two adjoining semis are replaced by a
pair of garden flats with a pair of duplexes
above. All four homes have their own front
door to the street and direct access to a
private garden, and the duplexes also have
large roof terraces. The floorspace of the
flats is 104 sqm and the duplexes are 130
sqm: all are generous family homes with
space for three or four bedrooms.
25
Scenario 4 - two become four
Two adjoining semis are replaced by a pair
of ground floor and basement duplexes
with a pair of duplexes above. All four
homes have their own front door to the
street and direct access to a private garden
or large roof terrace. The floorspace of
the lower duplexes is 160 sqm and the
upper duplexes are 125 sqm: all are
generous family homes with space for
four bedrooms or more.
The cost of basement excavation and
construction make this scenario more
suitable for higher value areas.
26
Scenario 5 - two become six
Two adjoining semis are replaced by a small
three-storey block of six flats. Ground and
first floors flats have three bedrooms, at
least 86 sqm floorspace and direct access
to a private garden. Second floor flats have
two bedrooms and 70 sqm floorspace.
On suitable sites, this scenario will yield the
most homes and the highest financial value
to the existing owner.
27
Scenario 6 - 12 become 24
This shows all of Scenarios 1 to 5 combined in a single
suburban block and interspersed randomly with retained
semi-detached houses. It also shows that Scenarios 1 and
28
3 could be combined. The overall impact is sympathetic to
the existing scale and grain of the neighbourhood.
Draft Design Guide for Semi-Permitted Development
To be effective, Permitted Development must not be
hampered by over-complex rules or a subjective approvals
process. On the other hand, a few simple rules can ensure
that a decent standard of design is achieved. These need
to be measurable, easily understood by the applicant
and easily checked by the approved inspector. Permitted
development should improve the appearance and
sustainability of its setting, not damage them.
6.Front gardens and car parking
We believe the suburban street scene should be
dominated by greenery not cars. We show hardstandings covering no more than 50% of the front
garden area, and openings for car access no more
than 3.0m wide, leaving most of the frontage for
hedging.
The objective is to promote ‘good ordinary’ design,
which will stand the test of time – and to prevent bad
design. Following rules cannot in itself achieve awardwinning outcomes or ground-breaking innovation. Other
satisfactory solutions – and maybe better ones - may well
be possible, but will require planning permission in the
normal way.
So, we propose to draft and test a simple design guide
covering the following headings – the final version would
be put to the GLA for endorsement and adoption as a
Supplementary Planning Document. It would include
guidance on the following topics. We have added in italics
the assumptions made in our sample Scenarios, which
generally adopt a conservative approach.
1.Building lines and distance between facing
habitable room
Our scenarios follow the existing building lines
to the street and maintain at least 20m between
facing rear windows.
2.Height and massing in relation to the prevailing
eave and ridge heights in the area
Our scenarios build no higher than existing ridge
heights. We use mansard roofs set-back behind
parapets to increase second floor accommodation.
3.Gardens and terraces
Every home in our scenarios has a generous
private outdoor space. Gardens are at least 30sqm
and roof terraces are larger than London Plan
standards.
4.Internal space standards
Our scenarios focus on family homes and show
internal areas larger than London Plan standards.
5.Basements
Our scenario 4 includes ground and basement
duplexes. We propose that wholly basement flats
should be disallowed.
Example of measurable design rules
7.Refuse stores and cycle parking
Semi-permissive development is an opportunity
to counter bin blight. The discrete integration of
refuse storage and cycle parking takes precedence
over the provision of on-plot car parking.
8.Mechanical and electrical kit
Semi-permissive development is an opportunity to
counter blight from pipes and wires by minimising
the allowable kit visible from the street.
9.Roof and wall materials
Semi-permissive development could stipulate
a durable palette of traditional materials and a
prohibited list of those which easily degrade.
10. Side passages
The gap between semis is a key aspect of their
character and utility. However, where there is
sufficient width to meet access requirements, it
is acceptable to enclose the side pas-sage with a
single-storey infill subordinate to the main building.
29
Sample Development Appraisal
By way of example we have tested the financial viability
of Scenario 3, which replaces one pair of semi-detached
houses with two duplexes and two flats. This is likely to
be one of the more financially challenging options, but it
passes the test and incentivises the owners with £200,000
profit. By comparison, Scenario 1 is easy, because it
involves no demolition, and Scenario 5 will generate the
most value.
There are many ways in which collaborating owners could
develop their combined plots and create new and improved
homes. They may want to occupy one or more of the new
homes themselves and sell the others, or they may want to
move elsewhere and sell or rent them all.
Enterprising and equity-rich pairs of householders could
fund and carry out their own development. Some may
group together to create larger co-housing projects. Others
will turn to the market, which will respond with funding and
development packages increasing the speed and scale of
change. Developers can offer streamlined services based
on a standardised set of designs, which would also lend
themselves to consumer choice through custom-build.
Small is beautiful
30
In order to test the financial viability of Semi-Permissive
we have assumed a scenario whereby a developer
contracts with the owners to fund and carry out all the
development work. On completion the developer pays the
full market value of the original houses (now demolished)
and shares the development profit with the owners. Owners
can also choose to swap their original equity for one of the
new properties: this would reduce development risk and
sales costs.
This scenario provides the owners with maximum return
for minimal effort and minimises stamp duty and finance
costs. The downside is that the owners need to fund their
own alternative accommodation during the development
period: alternative scenarios can provide some or all of
the plot value up-front, enabling the owners to buy or rent
elsewhere, but would reduce the profit margin.
The main influence on viability and profit level is the
additional amount of floor space and added value of the
new homes in comparison with the old ones. Clearly the
differential will be greatest where the existing plots are
under-developed and the houses are in poor condition. For
this exercise we have assumed average conditions and a
typical mid-value location.
Image courtesy of www.acrylicize.co.uk
Development income
Two garden flats @ 1200 sqft each
valued at £570,000
Two duplexes @ 1400 sqft each
valued at £665,000
1,140,000
1,330,000
Gross sales value2,470,000
Sales, marketing and legal costs @2.5%
(62,000)
Net income2,408,000
Land cost
Two semi-detached houses @1450 sqft each
valued at £550,0001,100,000
Legal costs assuming deferred payment
and no SDLT15,000
Total
1,115,000
Planning costs
Affordable housing contribution@ £20,000
per additional home40,000
Car club contribution5,000
Professional fees10,000
Total55,000
Works costs
Demolition and enabling works
25,000
Construction @ £1500 per sqm 725,000
Fees and miscellaneous costs @ 10% 75,000
Finance costs @7.5% based on 15 month
cashflow including void period
31,000
Total856,000
Outcome
Development income2,408,000
Combined development costs
2,026,000
Gross surplus382,000
Developer’s margin @ 20% of planning
and works costs182,000
Additional profit allocated to owners 200,000
31
16 ideas for transforming Metroland
The original report, “Supurbia: a study in urban
intensification in Outer London” was produced by HTA
Design LLP in 2014.
The study showed how urban intensification of suburban
London might contribute to an increase in housing supply,
promote economic activity, improve local service provision
and reduce congestion – whilst improving the quality
of life, the choices available and the sustainability of
the suburbs.
The study suggested that giving suburban householders
a vested interest in development could help to overcome
resistance to change. It contended that doubling the
density of just 10% of the outer London Boroughs could
create 20,000 new homes per annum.
But how might such changes be triggered, what incentives
might begin to unlock the potential? Is there a case for
special measures based on the principle of Housing Zones
proposed in the GLA’s Housing Strategy? Or should the
incentives be more generally applied across the outer
Boroughs and London as a whole? The study made 16
preliminary proposals for further discussion. Many of
these have been developed further in this latest report
and in submissions to the NLA’s New Ideas for London
Insight Study.
Here is the list in full.
32
1.Suburban intensification zones
Designation of priority status for areas of poor
environmental quality, and high levels of social
deprivation and fuel poverty. A planning policy framework
for intensification including enhanced permissible
development rights, relaxation of density limitations
and restrictions on development in gardens. Area based
collaboration integrating contributions from the local
authority social landlords, private housing developers,
and energy providers, amongst others. Pre-negotiated
development agreement for standard intensification
typologies (pattern books).
2.Redevelopment of high street frontage
Development of high quality homes for millenials and
downsizers following HAPPI principles in locations
close to appropriate services. Significant increase in
residential densities (doubling or trebling) and
re-provision of smaller amounts of retail floorspace
that can be serviced from the street, liberating rear
service areas for conversion to high quality shared public
realm. Improvements to public realm, provision for
shared transportation – mobility scooters, electric
bikes and cars.
3.Planning consent through Local Development Orders
and Plot Passports
Enable co-housing and custom build projects by
collaborating neighbours through planning legislation
creating permitted development opportunities as
described in the plot passports (referencing the preapproved pattern books) in consenting neighbourhoods.
Local Authorities promote such incentives through Local
Development Orders. Over time, some communities may
adopt Neighbourhood Plans to encourage intensification
which would lead to area based referenda based on
mutual consent.
4.Local Pattern Books
Use of pattern books (developed by local architects,
possibly for a royalty fee) for new homes which are
compliant with modern building regulations, life time
homes principles and national space standards. Based
on the typological uniformity of the archetypal semidetached suburbia, a range of standard typologies
(possibly prefabricated, at least in part). The range of
solutions would include roof and rear extensions, mews
houses and gap infilling types. The Pattern Books can be
referenced in the plot passport.
5.Custom build
Packaged development service for purchasers of
high quality, branded manufactured homes, including
site acquisition, choice of appropriate mortgages,
manufactured home showroom, site and service
preparation, pre-negotiated framework agreements with
LPA for approved types.
6.Car sharing
Set up local fleet companies to hire out electric only
vehicles and e-bikes on a large scale. Encourage
homeowners to ditch owning their cars and use the fleet
cars and bikes instead. Offer them an allotment outside
their home where their car-parking space used to be.
7.Public realm improvements
Phased reduction in space allocated to cars in
private ownership alongside take up of modal shift to
sustainable transport and car/bike/mobility scooter
sharing. Introduction of street trees and biodiverse green
infrastructure and creation of new micro parks on unused
parking spaces due to an increase in car sharing. Create
cycle lanes following a reduction in street car parking
by 50%. Turn some streets into linear parks with games
areas, trees and play spaces for toddlers.
8.Neighbourhood concierge
Local corner shop or cafés to expand to deliver a
neighbourhood concierge to accept deliveries, keep keys,
arrange dry cleaning or house cleaning and to include a
Swap Shop (based on collaborate consumption principles
for hiring out / swapping sporting equipment, DIY tools,
photographic gear, fitness equipment, etc)
9.Zero carbon new homes
Build super-efficient homes that minimise the impact
on the energy and water grids. This will save money by
saving the cost of additional infrastructure that is always
needed on greenfield sites. These homes need no new
roads, sewers, power lines or drains, they already exist.
10.Carbon budget
Give each plot a carbon budget to spend, which enables
them to trade amounts emitted between the new and
the existing homes. Link it to local taxation. Reduce
the budget over time to make sure that the homes are
maintained and upgraded.
11.Retrofitting
Encourage the improvement of the energy efficiency of
the existing buildings to make space in the infrastructure
grids for new homes.
12.Neighbourhood water management scheme
Water usage and waste streams should be reduced
to minimise the impact of the new development on
sewer and drainage systems. By building efficiently
and by retrofitting improvements to the existing stock
we can remove the need to install new and expensive
infrastructure. Low water use appliances, Sustainable
urban drainage, using rainwater to irrigate gardens and
recycling systems are all practical methods that can
be applied.
33
13.Neighbourhood Energy Storage
Create large battery storage nodes near substations to
enable local enterprises to generate and store energy
locally where it is needed most. Use roof-mounted PV
systems, local car park areas, roofs of supermarkets and
businesses to site PV arrays. Encourage locals to use
the energy when it is cheaply available by selling stored
energy at a low rate.
14.Drone delivery
Set up a drone delivery company to deliver the myriad of
small packages coming from online shopping. Reduce the
daily traffic in the suburbs substantially and improve air
quality at the same time.
15.Ban combustion
Introduce a boiler replacement drive where gas
combustion is replaced by air source heat pumps
as homes are upgraded. With the car hire replacing
combustion engines this will remove pollution from the
suburbs for good, reducing noise, improving air quality,
improving health and the desirability of city life.
16.Internet of things
Use the local energy storage enterprise to set up an
Internet of Things network to enable energy savings to
be maximised. Freezers that shut down at peak times
to save power at no risk, electric vehicles that charge
themselves when there is a lot of renewable energy,
washing machines and dishwashers that turn themselves
on when its cheapest to run a wash.
34
Conclusion
We propose one or more pilot studies in collaboration with
participating Local Authorities, where we intend to explore
the possibilities of these approaches based on realistic
assessments of actual and potential value. We recognise
that the piecemeal nature of ownership in London’s
suburbs means that the outcome would need to be capable
of supplying sufficient yield for the owners of such property
to create the necessary incentive for change.
We envisage area based schemes, centred on underdeveloped transport hubs where urbanisation in a
concentric pattern could create outward moving contours
of increased value, like the ripples in a pond, triggering
the take up of intensification schemes in a variety of
typologies which we will explore and illustrate. Our hope
is that we can postulate a viable scenario for processes
capable of transforming the poorer, often subtopian areas
of suburbia into a vision of thriving, vibrant and sustainable
placemaking – a vision of Supurbia!
Creating value in Suburbia
The place potential of well-connected areas of metroland
makes possible value uplift associated with conversion to
Supurbia significant.
The map below shows Savills model of value uplift
potential in London, it shows some of the greatest
potential is in suburban outer London.
London’s value uplift potential
This map shows the difference between the modelled
potential flat values and existing flat values. The darker
the red areas, the greater the potential for regenerative
development to unlock market value uplift and achieve the
modelled flat values. In these areas, there is likely to be a
barrier to reaching higher values. In order to achieve value
uplift, this barrier will need to be removed. There needs to
be a catalyst to remove this barrier, which could be either a
transport improvement or high standard placemaking. The
creation of Supurbia from Suburbia may be part of this.
The places in closest proximity to central employment
locations are likely to see value uplift before more distant
locations so it would seem best to locate the parts of
metroland that are closest to faster transport nodes.
35
London’s Density potential
In addition to this place potential, the potential increase in
housing density means gross development values (GDVs)
per hectare should increase substantially.
A worked model of the Supurbia site shows that using a
conventional developer model to achieve it yields a lower,
though not unrespectable margin of 21% after the costs of
land acquisition and development. Land acquisition under
conventional models would however be lengthy, difficult
and fraught with problems. If one landowner is unwilling to
sell, it could scupper the whole scheme and cost a great
deal of money. Significant premiums would probably need
to be paid for units in order to incentivise owners to sell.
If owners themselves are incentivised to club together in
groups around each building group of, say 8 properties,
the uplift they could see on the gross development value of
their new buildings could be in the region of 60%. This is
because they would not have to acquire their site.
As owners, they would be landowner developers.
The table shown is a roughly worked case study of
the Supurbia site and shows that the density uplift is
significant (from 25 units per hectare to 59 units per
hectare) and that, even without place quality uplift, the
potential returns to the owners of the typical 3 bed semis
in the area should be significant enough to act as a strong
incentive for development.
36
This begs the question as to what sort of development
vehicle would be needed for owners to realise this uplift.
Three elements would appear essential:
• 100% agreement of neighbours in groups of houses
capable of enabling development and land equalisation
agreements in advance of development to share the
benefits of cooperation equitably.
• Group self-procurement mechanisms with trusted
providers to minimise development risk.
• Mechanisms to minimise capital outlay by landowners
until units are sold or mortgaged. This might be secured
on land or built property value by custom house builders.
Hectares
Current
housing
units per
hectare
Suburbia
1.58
25
Supurbia
1.58
59
Less build
costs
Current
value per
hectare
Gross
development
value per
hectare
After all
costs
£14.8m
£53.2m
£33.1m
Developer’s
margin
21%
Owner
occupier’s
self procured
margin
62%
Credits
HTA Design LLP
Ben Derbyshire, Managing Partner
Contact: [email protected]
Pollard Thomas Edwards
Andrew Beharrell, Senior Partner
Riette Oosthuizen, Partner, Planning
Hoi Yat Tsoi, Associate
Alexis Butterfield, Associate
Tim Metcalfe, Associate: Communications Manager
Rory Bergin, Partner, Sustainable Futures
Lucy Smith, Partner, Communications Design
Scott Adams, Head of Urbanism
Rachel Hardman, Marketing Manager
Melanie Forster-Nel, Architect
Nerea Bermejo, Illustrator
106-110 Kentish Town Road
London NW1 9PX
020 7482 8016
www.hta.co.uk
@HTADesignLLP
Savills
Yolande Barnes, Director, World Research
Nathaniel Lichfield and Partners
Pauline Roberts, Planning Director
Thanks to:
Peter Murray, New London Architecture
David Lunts, GLA
John Lett, GLA
Mark Lucas, London Borough of Redbridge
John Miller, London Borough of Lewisham
Kathryn Firth, PUBLICA
Marc Vlessing, Pocket Living
Diespeker Wharf
38 Graham Street
London N1 8JX
020 7336 7777
www.pollardthomasedwards.co.uk
@PTEarchitects

TRANSFORMING SUBURBIA SUPURBIA SEMI

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